Likely in the senses “probably destined” and “probably” is often preceded by a qualifying word like very, more, or quite: The board is very likely to turn down the request. The new system will quite likely increase profits. However, despite statements to the contrary in some usage guides, likely in these senses is standard without such a qualifier in all varieties of English: It will likely be a bitter debate. The shipment will likely arrive on Thursday. See also apt, liable.

likely

(usually foll by an infinitive) tending or inclined; apt: likely to rain

2.

probable: a likely result

3.

believable or feasible; plausible

4.

appropriate for a purpose or activity

5.

having good possibilities of success: a likely candidate

6.

(dialect, mainly US) attractive, agreeable, or enjoyable: her likely ways won her many friends

adverb

7.

probably or presumably

8.

as likely as not, very probably

Usage note

Likely as an adverb is preceded by another, intensifying adverb, as in it will very likely rain or it will most likely rain. Its use without an intensifier, as in it will likely rain is regarded as unacceptable by most users of British English, though it is common in colloquial US English

c.1300, perhaps from Old Norse likligr "likely," from likr "like" (see like (adj.)). Old English had cognate geliclic. Meaning "having the appearance of being strong and capable" is from mid-15c., though now mostly confined to American English; according to OED this sense is perhaps influenced by like (v.). Sense of "good-looking" is from late 15c. Meaning "probably" is attested from late 14c., now principally in American English.

LIKELY. That may be liked; that may please; handsome. In the United States, as a colloquial term, respectable; worthy of esteem; sensible.--Worcester. [Bartlett]